Similar to a Brain Ninja, a Brain Pirate stays in someone's mind much longer, usually pillaging and taking over that person's thoughts. This can be used to describe women that you sometimes can't stop thinking about.

Mike: Dude, I can't stop thinking about Ashley.
Steve: Why? You like her?
Mike: I'm Freakin' in LOVE with her.
Steve: I don't blame you, that Ashley can be a HUGE Brain Pirate sometimes...